U.S. patent application number 09/751893 was filed with the patent office on 2002-10-24 for mobile microwave oven.
Invention is credited to Stutman, Peter S..
Application Number | 20020153370 09/751893 |
Document ID | / |
Family ID | 32658764 |
Filed Date | 2002-10-24 |
United States Patent
Application |
20020153370 |
Kind Code |
A1 |
Stutman, Peter S. |
October 24, 2002 |
Mobile microwave oven
Abstract
A mobile, low powered microwave oven is disclosed. The oven has
top entry to the heating chamber, it is powered from the cigarette
lighter, has the controls and display and the cooling vents also on
the top surface of the oven. The oven is arranged to be secured to
the seat by the seat belts in such a manner that the oven will
operate while so secured. There is also a spill container in the
heating chamber. Materials may be used that make the oven cabinet
transparent.
Inventors: |
Stutman, Peter S.; (Sudbury,
MA) |
Correspondence
Address: |
Peter S. Stutman
27 Lillian Avenue
Sudbury
MA
01776
US
|
Family ID: |
32658764 |
Appl. No.: |
09/751893 |
Filed: |
December 29, 2000 |
Current U.S.
Class: |
219/715 ;
219/756 |
Current CPC
Class: |
B60N 3/16 20130101; H05B
6/6426 20130101 |
Class at
Publication: |
219/715 ;
219/756 |
International
Class: |
H05B 006/80 |
Claims
What is claimed is:
1. A low-power microwave oven capable of operating from the DC
power normally available in passenger vehicles and boats through
the "cigarette lighter" or "accessory power" socket and having
means of using a seatbelt to secure the microwave oven in a seat of
a vehicle, comprising; A compact microwave oven cabinet enclosing a
cavity or heating chamber, whose walls are constructed of a radio
reflecting material such as metal sheet, having a similarly
constructed door allowing access to the cavity, a source of
microwave energy, a magnetron, suitable for operation at the power
levels described, receiving power at appropriate voltages from a
switching power supply deriving its power from the vehicle
"cigarette lighter" or "accessory power" socket.
2. Means for the microwave oven described in claim 1 with its
control keypad and display, and cavity door, on the same top
surface such that they may be easily accessed while the microwave
is secured in a seat of a vehicle and so that food may be easily
placed into, and removed from, the microwave oven cavity. Cooling
air intake and outlet on the same top surface so they are not
blocked, occluded, ,nor airflow through them impeded, by proximity
to the seat components or other structures.
3. The microwave oven described in claim 2 with a DC motor having
affixed to its shaft a set of fan blades and positioned so as to
intake air from a top surface mounted vent and plenum, propel the
air through the magnetron anode cooling structure and then through
an additional plenum out another top surface mounted vent.
4. The microwave oven described in claim 3 with a voltage regulator
always on when the device is connected to the vehicle power source,
providing power at appropriate voltage for the various logic and
control circuits.
5. The microwave oven described in claim 4 with a solenoid operated
locking mechanism to prevent the cavity door from springing open
while the vehicle is in motion and thus releasing microwave energy
into the vehicle.
6. The microwave oven in claim 5 with a means, a detented stud, of
retaining molded "microwave safe" food containers with locking lids
and appropriate vents in place while a vehicle is in motion by
means of a mating cavity or other retaining structure molded in to
the bottom of the food container.
7. The microwave oven in claim 6 with a removable molded,
radio-transparent, heat-resistant, dishwasher-safe plastic liner
constructed to fit closely into the microwave oven cavity and
covering the bottom except for a clearance hole for the detented
stud and extending most of the way up the sides of the cavity, but
open at the top.
8. The microwave oven in claim 7 with a different removable molded,
radio-transparent, heat-resistant, dishwasher-safe plastic liner
constructed to fit closely into the microwave oven cavity and
having an inverted pyramidal well into which food heating
containers may be placed so as to be constrained from movement
while the vehicle is in motion.
9. The microwave oven in claim 8 with a digital system controller
consisting of a microprocessor, adequate RAM and ROM and input
buffers and output drivers which monitors acceleration signals from
an accelerometer or similar spatial displacement measuring devices
as well as cavity door and over temperature interlocks and other
sensors related to safety concerns, and which causes immediate
system shutdown in the event of a hazardous or fault condition.
10. The microwave oven in claim 9 with an algorithm to multiply a
"standard" heating time for a typical full-size kitchen microwave,
and input to the system controller input via the control keypad, by
a factor properly compensating for the lower power output and
consequent longer heating time required in this lower-power
microwave oven.
11. The microwave oven in claim 10 with a DC motor driving a
cooling fan for a magnetron supplied with power directly from the
vehicle via a transistor switch and whose intake and exhaust
airflow is contained within plenums vented to the outside of the
cabinet.
12. The microwave oven in claim 11 with a means of monitoring input
voltage and input current to the system and causing system shutdown
in the event that the vehicle battery voltage drops below an
acceptable level or if the current being drawn rises near a level
which will cause the vehicle power outlet fuse to blow or which is
otherwise unacceptable.
13. The microwave oven in claim 12 with a carrying handle molded
into the top surface or externally affixed thereto so as to not
interfere with any other required functions.
14. The microwave oven in claim 13 with an external cabinet or
housing constructed of a transparent or translucent material which
allows viewing of the internal components and construction.
15. A low-power mobile microwave oven for use in a vehicle or boat
comprising; a cabinet enclosing a cavity or heating chamber, whose
walls are constructed of a radio reflecting material such as metal
sheet, a magnetron for providing microwave energy to the heating
chamber, a switching power supply that supplies energy to the
magnetron, means for supplying power to the switching power supply,
and wherein the cabinet defines a top surface, wherein the controls
for the oven, a control keypad and display, the cooling air inlets
and outlets and a door that provides access to the heating chamber
or cavity are all provided on the top surface.
16. A low-power mobile microwave oven for use in a vehicle or boat
comprising; a cabinet enclosing a cavity or heating chamber, whose
walls are constructed of radio reflecting material such as metal
sheet, and wherein the cabinet contains a door that provides access
to the heating chamber, controls for the oven, a control keypad and
display, and air inlet and outlets, a magnetron for providing
microwave energy to the heating chamber or cavity, a switching
power supply that supplies energy to the magnetron, a plug and
cable from the "cigarette lighter" or "accessory power" socket or
similar connector for supplying power to the switching power
supply.
17. A low-power mobile microwave oven for use in a vehicle such as
a car, a boat, or an aircraft, wherein the vehicle contains seat
belts, comprising; a cabinet enclosing a cavity or heating chamber,
whose walls are constructed of a 'radio reflecting material such as
metal sheet, and wherein the cabinet contains a door that provides
access to the heating chamber, controls for the oven, a keypad and
display, and air inlets and outlets, a magnetron for providing
microwave energy to the heating chamber, a switching power supply
that supplies energy to the magnetron, means for supplying power to
the switching power supply, and means for securing the oven to a
seat by the seat belts.
18. A low-power mobile microwave oven for use in a vehicle or boat
comprising; a cabinet enclosing a cavity or heating chamber, whose
walls are constructed of radio reflecting material such as metal
sheet, and wherein the cabinet contains a door that provides access
to the heating chamber, controls for the oven, a control keypad and
display, and air inlets and outlets, a magnetron for providing
microwave energy to the heating chamber or cavity, a switching
power supply that supplies energy to the magnetron, and means for
supplying power to the switching power supply wherein the total
power consumption is less than 300 Watts.
Description
RELATED APPLICATIONS
[0001] The present application claims priority from U.S.
Provisional Patent Application, entitled Mobile Microwave Oven,
Ser. No. 60/173,679, which application was filed on Dec. 29, 1999,
by Peter S. Stutman, a U.S. citizen, of 27 Lillian Avenue, Sudbury,
Mass., 01776 and which provisional is hereby incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] This invention generally relates to microwave ovens and more
specifically to microwave ovens for use in vehicles such as cars,
trucks, and boats. It has features specific to operation from a
standard DC power source found in such vehicles as well as features
which mechanically secure it within the vehicle.
BACKGROUND OF THE INVENTION
[0003] Microwave ovens designed for portable operation and
operation in vehicles have been proposed previously. U.S. Pat. No.
4,667,075 of Sakurai proposes using a three-phase AC alternator to
supply power. U.S. Pat. No. 5,276,300 of Low et al, describes a
microwave oven containing essentially an inverter to allow 12 volt
DC operation. AGOR technologies of Verson, France manufactures a
similar product. These devices, operated at power levels of about
0.6-1.0 kW nominal require DC input currents from a 12 volt source
of approximately 100 amperes. This much current requires direct
connection to the vehicle battery with very heavy gauge wire or the
dedicated alternator of Sakai and implies mechanical and electrical
installation skills beyond the range of the average consumer. The
oven must also be somehow mounted to the vehicle so that it does
not move around. The microwave ovens previously described are
mechanically very similar. They feature a cavity with a front
opening door; that is, with a vertical hinge. The timer and control
keypad is mounted vertically in proximity to the door and they are
very similar to or modifications of conventional consumer microwave
ovens.
[0004] Conventional consumer microwave ovens have power ratings in
the 500W-1000W range. These ratings represent the power delivered
into the oven cavity. The nameplate power consumption of these
microwave ovens is typically 50-75% higher. For example a Magic
Chef MC-03JS Compact Microwave oven is rated at 500 Watts and is
rated at a power consumption of 750 Watts. While these ovens could
be powered by a DC to AC inverter of appropriate output, the
inverter would have to be hardwired with heavy gauge wire, such as
No. 0, to the vehicle battery or alternator in order to receive the
necessary current. If we assume a 90% inverter efficiency the 500
Watts oven mentioned above would cause a typical inverter to draw a
current of about 60 amperes at a nominal 13.8 volts.
SUMMARY OF THE INVENTION
[0005] This invention is a small, low-power, approximately 200 Watt
magnetron-type microwave oven. The invention described herein is
designed to be powered by a vehicle's "accessory power" or
"cigarette lighter" jack and to be held in place on a seat by a
standard vehicle seat-belt. Also described is an upward-opening
door and plastic radio-transparent microwave cavity liner designed
to contain spilled foods and facilitate cleaning. Methods of
retaining food containers which hold the foods being heated, as
well as other safety and convenience features useful for real-world
operation in the mobile environment are described.
[0006] It is envisioned that the device described will find wide
application in cars, trucks, recreational vehicles, boats and
simple living situations which do not provide conventional AC mains
and in which consumers are unlikely to perform or have performed
involved installations. It can be used for many tasks, from heating
baby bottles and meals in properly designed containers, to heating
the morning's coffee, to warming automotive gasket materials in
cold climates during repair operations.
[0007] In the preferred embodiment, a high frequency switching
power supply generates the required filament and high voltage
necessary for magnetron operation. This is more efficient than
suffering DC/AC inverter losses in addition to the losses seen in
the typical microwave oven power transformer. The magnetron is the
type whose magnetic field is generated by permanent magnets.
[0008] The only readily available electrical outlet or jack in most
modem cars and trucks and smaller boats is the familiar "cigarette
lighter" or "accessory power" socket. This socket is familiar to
millions of users who power mobile phones, radar detectors, small
inverters and other convenience devices from them. These jacks are
typically fused at 15-30 amperes. This limits total electrical
power input to the microwave oven described here to a range of
approximately 200-400 Watts. This corresponds to a typical
microwave power rating of about 125-250 Watts. Most users of
microwave ovens are used to larger power inputs as mentioned
previously. Therefore the cooking time in this low power microwave
oven will be longer than the "standard" times experienced in
larger, more powerful units. For example, if it takes 1 minute to
heat a cup of soup to serving temperature in a 750 Watt microwave
oven found in a typical American kitchen, it will take three
minutes nominally in a 250 Watt unit. In fact, given the
significant increase in cooking times, there will be thermal losses
including radiational and convective losses which will tend to cool
the food being heated and which will lengthen the required time
beyond the simple ratio of power. In one mode the invention
described here takes the "standard" cooking time for a 750-900 Watt
microwave oven and automatically multiplies it by an appropriate
factor to arrive at the correct heating time for this lower-power
oven. In another mode the user enters a desired heating interval
which is not multiplied by any factor.
[0009] The invention described herein also senses input current and
voltage. It shuts down if excessive current is drawn to protect the
"accessory socket` fuse or if voltage drops to a level just above
that which corresponds to the vehicle battery being unable to start
the vehicle.
[0010] A microwave oven, even a small one, is a substantial mass,
and it may contain foods which are near or at the boiling point. It
must be securely mounted within the vehicle cockpit, such that in
case of an emergency maneuver, sudden acceleration, or crash, it
does not fly about the cockpit causing injury or burn hazards to
passengers nor damaging other components of the vehicle. The
present invention has split loops affixed to the outside of the
cabinet which facilitate securing the microwave oven in a seat with
the seatbelt much as a child's safety seat would. In the event of a
collision the microwave oven described here shuts down. It also has
the usual safety features such as door interlocks and
over-temperature sensors found in virtually all consumer microwave
ovens. Conventional mounting points are provided for situations in
which the device may be bolted down.
[0011] The invention described herein also places the intake and
exhaust for the cooling air required by the magnetron on the top
surface such that the airflow is not impeded as it would be if
mounted on a seat with downward or side facing intakes and
exhausts. The keypad is also mounted on the top surface for easy
access.
[0012] The invention described herein also has an upward opening
door allowing access to the oven cavity. The cavity has a
radio-transparent, removable, easily cleaned, plastic liner made of
heat resistant plastic which contains any spills which may occur.
These two features help insure that even if food somehow should
spill within the oven, that it will not leak out into the vehicle
cabin. The door is retained shut by a locking mechanism when the
oven is in operation and may stay in that state until an unlock
button is pushed on the unit's keypad.
[0013] Since the vehicle may be in motion while the invention is in
use, means must be provided of fixing the food container in place
so that it does not "bounce around" and spill its contents nor
damage the cavity walls. In the preferred embodiment, a detented
stud is centrally affixed to the center of the carousel. There are
mating cavities molded into "microwave safe" plastic heating
containers with locking lids and appropriate vents. The food is
placed into the container, the vented lid is affixed with a
latching lip or similar arrangement, and the cavity, typically in
the center of the container is pressed down onto the detented stud
which retains it in place. Food portions in disposable heating
containers, such as "Chef Boyardee.RTM. Lasagna, Microwave Meals,
(10.5 oz. size)" can be manufactured with the appropriate mating
cavity molded in.
[0014] Alternatively an inverted pyramidal well is molded into a
radio-transparent, heat resistant plastic support sheet. Food in
appropriate containers is placed down into the well until contact
is made with the walls of the well. Alternatively a curved
non-metallic spring-loaded radio-transparent wall could be used as
retention device.
[0015] A carrying handle is molded into the top surface to
facilitate handling of the mobile microwave oven. A DC input cable
terminated in a "cigarette lighter" plug or other suitable
connector of sufficient length and sufficient gauge is provided so
that the invention may be installed in the back seat of long
vehicles while being plugged into the "cigarette lighter" or
"accessory socket" which is usually proximal to the vehicle's front
seat.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1: Mobile Microwave Oven
[0017] FIG. 1A: Keypad for Mobile Microwave Oven
[0018] FIG. 2: Mobile Microwave Oven Interior
[0019] FIG. 3: Mobile Microwave Oven Door, Door Locking Solenoid,
and Interlock
[0020] FIG. 4: Mobile Microwave Oven System Diagram
[0021] FIG. 5: Inverted Pyramidal Food Retainer and Cavity
Liner
[0022] FIG. 5A: Food Container Retention Stud
[0023] FIG. 6: View of Mobile Microwave Oven in Seat Retained by
Seatbelt
[0024] FIG. 7: Side View of Mobile Microwave Oven in Seat Retained
by Seatbelt
[0025] FIG. 8: Mobile Microwave Oven Operational Flowchart
DETAILED DESCRIPTION OF DRAWINGS
DESCRIPTION OF SYSTEM
[0026] The LOW-POWER MOBILE MICROWAVE OVEN is typically placed on a
passenger seat. On its top surface are the CONTROL KEYPAD AND
DISPLAY (60), the magnetron COOLING AIR INTAKE (80) and OUTLET
(110), and the upward opening microwave CAVITY DOOR (160) affixed
by HINGE (150). The HINGE (150) can be positioned on any of the
four sides of the MICROWAVE CAVITY (120) opening in The door seals
the cavity so as to contain all microwave energy by means of
conductive elastomeric GASKET (210) and conventional choke seal
design.
[0027] The mobile microwave oven CABINET (200) is secured in place
on the seat by running the seatbelt for that seat through the SPLIT
LOOPS (190) attached to the CABINET (200). The waist portion of the
seatbelt is tightened to secure the CABINET (200) in place. The
SPLIT LOOPS (190) are angled down from the vertical plane toward
the seatback so as to facilitate force components acting on the
CABINET (200) down toward the seat cushion and backward toward the
seatback without kinking or narrowing of the belt where it passes
through the SPLIT LOOPS (190). This method is similar to that used
to secure infant and child safety seats in vehicles. Alternatively,
angle brackets and screws suitably attached to the CABINET (200)
can be used to effect a permanent mounting.
[0028] The "cigarette lighter" or "accessory power socket" PLUG
(10) is inserted into the vehicle's "CIGARETTE LIGHTER" or
"ACCESSORY" socket. A two-conductor insulated POWER CABLE (15) of
at least #8 gauge attached in series with the plug (10) brings
power into the microwave oven's cabinet (200). This positive lead
of this nominal 12 VDC power passes through the current sensing
shunt (20) and is then bussed to the voltage regulator (30), the
input of the switching power supply (40), and the input of the
Input voltage sensor comprised of A/D converter (70). It is also
connected to the DC fan motor control switch (95) and the door
locking solenoid switch (185), and the oven cavity lamp switch
(125). The 12 VDC rating in a vehicle is nominal and is usually
closer to 14 VDC when the vehicle engine is above idle speed
[0029] The voltage regulator (30) is a simple series pass regulator
which outputs +5 VDC at sufficient current to operate the system
controller (50), the keypad/display (60) and associated components.
Its devices have voltage ratings which are suitable for use in the
automotive electrical environment and will survive the transients
known to exist in this environment.
[0030] The switching power supply (40) is an inverter type
switching power supply with a 12 VDC nominal input. It outputs the
magnetron filament power, typically about 3 VDC at several amperes
as well as the B- voltage, typically about 2-4 kV and in this
application about 75-100 mA at 2 kV. The exact voltages depend on
the specific characteristics of the magnetron (100). The magnetron
anode is typically grounded to the microwave oven case (200) and
the cathode to anode potential necessary for operation is developed
by depressing the isolated or "floating" cathode filament below
ground potential with the negative voltage. The magnetic field of
the magnetron is generated by permanent magnets integral with its
housing. While magnetrons operating at the typical 2450 MHz
frequency have been used in a prototype of this invention, other
frequencies might be employed to optimize energy transfer into or
energy modes in the microwave oven cavity. The switching power
supply (40) utilizes inductive transformers whose wire windings,
insulation and other mechanical construction produce satisfactory
insulation and isolation so that the magnetron (100) filament can
be safely floated, and so that the high voltage output is not
compromised. The 3 VAC output is electrically floating and
connected with wires with insulation of adequate voltage
rating.
[0031] The switching power supply operates at a frequency much
higher than that of a typical AC line (60 Hz) and therefore
requires less energy storage on the output. Consequently the power
supply output can be keyed on and off very rapidly by means of the
PS (Power Supply) ENABLE SIGNAL from the System Controller (50). In
the preferred embodiment, the Power supply is driven by a PS (Power
Supply) CLOCK generated in firmware by the SYSTEM CONTROLLER (50),
alternatively a separate clock signal generator could be used.
[0032] The SYSTEM CONTROLLER (50) is a microprocessor with
associated RAM and ROM adequate for operation. Power is taken from
VOLTAGE REGULATOR (30) which also serves to isolate and decouple
the SYSTEM CONTROLLER (50) and related components from transients
that occur in vehicle power systems. Inputs to the SYSTEM
CONTROLLER (50) are Input Voltage Reading; Vr output by A/D
CONVERTER (70), Input Current Reading, Ir, developed by CURRENT
SHUNT (20) and A/D CONVERTER (75), the ACCELEROM signal output by
ACCELEROMETER (300), LOGIC CLOCK output by CLOCK GENERATOR (350),
INTERLOCK SIGNALS from the DOOR CLOSED INTERLOCK SWITCH (180) and
the OVER TEMPERATURE SENSOR (175) and KEYSTROKE DATA generated by
CONTROL KEYPAD AND DISPLAY (60).
[0033] Since this is a relatively low-power microwave oven, heating
times are longer than those of conventional, more powerful
microwave ovens typically found in kitchens. The invention
described here has power input to the cavity of approximately one
fourth of the power found in typical kitchen microwave ovens. Most
people who use a microwave oven are familiar with "standard"
heating times. These familiar times must be multiplied by a factor
of approximately four in order to be correct for the lower power
level in this invention. If a "standard" heating time is entered
via the CONTROL KEYPAD AND DISPLAY (60), the SYSTEM CONTROLLER (50)
multiplies the time by four in order to warm the food to the proper
temperature. Since longer intervals allow more cooling by radiation
and convection, a manufacturer might adjust the time further with a
lookup table or algorithm based on empirical results. A surface
pyrometer or other temperature sensor could also signal that
desired temperature has been reached.
[0034] The CONTROL KEYPAD AND DISPLAY (60) generates unique digital
signals in a format suitable for input to the SYSTEM CONTROLLER
(50), whenever a key is pressed. This subsystem also contains
display drivers which cause symbols and digits to appear in the
multi-segment multi-character alphanumeric display when appropriate
data is received from the SYSTEM CONTROLLER (50).
DESCRIPTION OF OPERATION
[0035] The Low-power microwave Oven is placed in a seat in a
vehicle. The waist belt portion of the seatbelt corresponding to
that seat is passed through the SPLIT LOOPS (190). The waist belt
is tightened down to secure the CABINET (200) in the seat.
[0036] The PLUG (10) is inserted into the "cigarette lighter" or
"accessory power" socket of the vehicle in order to obtain 12 VDC
power. The VOLTAGE REGULATOR (30) regulates the 12 VDC input to +5
VDC required by the SYSTEM CONTROLLER (50) and the CLOCK GENERATOR
(350).
[0037] The DOOR (160) of the MICROWAVE CAVITY (120) swings open on
HINGE (150). The user places the food or other substance to be
heated in a "microwave safe", radio-transparent heating container
with a locking vented lid. If the heating container has a mating
recess molded into the bottom, the container can be "popped" onto
the DETENTED RETAINER STUD (140). If there is no retaining
component on the heating container the PLASTIC LINER WITH INVERTED
PYRAMIDAL WELL (145), is used. This component (145) made of
radio-transparent, heat-resistant plastic, is simply placed in the
microwave oven CAVITY (120) in place of the PLASTIC LINER (130).
The food container described above is placed as far down into the
well as it will go, thus retaining it in most situations. The DOOR
(160) is closed, the SPRING LATCHING PIN (175) is captured by the
retaining RETAINING SPRING CATCH (170) and pressing on DOOR
INTERLOCK SWITCH (180) which closes, sending a logic level signal
to the SYSTEM CONTROLLER (50).
[0038] The user enters the length of time the food is to be heated.
If the user presses "STANDARD" on the "CONTROL KEYPAD AND
DISPLAY(60)", the SYSTEM CONTROLLER (50) multiplies by a factor
which compensates for the low-power feature of this microwave oven.
Typically this factor will be in the range of 2-6. If the user does
not press the "STANDARD" key, the time entered not multiplied and
represents the exact heating time.
[0039] The user presses the "START" key on the CONTROL KEYPAD AND
DISPLAY (60). The SYSTEM CONTROLLER (50) looks at all input signals
after receiving the "START" signal. The following signals must be
present:
[0040] INTERLOCKS: DOOR INTERLOCK SWITCH (180) actuated by closure
of cavity DOOR (160) in series with OVER TEMPERATURE SENSOR (175)
Pulls "INTERLOCKS" line to ground.
[0041] Vr: Voltage reading from A/D CONVERTER (70) must be above
minimum Acceptable battery voltage, nominally 11.5 volts.
[0042] Ir: Current reading from A/D CONVERTER (75) must be below
maximum current rating of power socket in vehicle. Set by
manufacturer as a function of intended usage, nominally 15 amperes
in a small car, as high as 30 amperes in some larger trucks.
[0043] If not all conditions are satisfied, a "BEEP" command is
sent to the piezoelectric annunciator to inform the user. If all
conditions are satisfied the SYSTEM CONTROLLER (50) begins the
heating of the food in its heating container. This is commanded by
outputting the following signals and causing the following
actions:
[0044] PS ENABLE: This signal enables SWITCHING POWER SUPPLY (40)
operation.
[0045] PS CLOCK: This signal drives the power switching circuits in
the SWITCHING POWER SUPPLY (40) thus supplying filament voltage 3
VAC as well as negative high voltage B- to the cathode
(filament).
[0046] MAG FAN ON: This signal drives the switch transistor (92)
which causes the DC FAN MOTOR to turn the attached FAN BLADES (85).
This draws air in through top-mounted cooling air intake and
circulates it through the attached PLENUM (82) past the DC FAN
MOTOR (90) through the MAGNETRON ANODE THERMAL RADIATOR (105) and
exhausts it via PLENUM (112) through top-mounted COOLING AIR OUTLET
(110).
[0047] LOCKDOOR: This signal actuates the DOOR LOCK SOLENOID (390)
by driving the switch transistor (395).
[0048] After the inputted time interval has elapsed the SYSTEM
CONTROLLER (50) ceases outputting all the signals necessary for the
heating to occur and the DOOR (160) is unlocked. If any of the
signals required by the SYSTEM CONTROLLER (50) are lost, (50)
ceases outputting the signals required for heating to occur.
[0049] The preferred embodiment described demonstrates the
advantages of the invention. Variations on the embodiment described
can be made to accommodate different installation configurations.
For example, the DETENTED RETAINER STUD (140) could be moved to one
of the four other stationary CAVITY (120) walls, enabling a
conventional "front-opening" microwave oven with a vertical HINGE
(150).
* * * * *